Abstract: A method of authenticating a polymer film comprises measuring the thickness of a layer therein by white light interferometry and/or measuring the birefringence of a layer therein. The method, and devices to carry out the method, may be used in security applications, for example to test for counterfeit bank notes.

Abstract: Authentication apparatus (1, 100) and methods which authenticate an item (4, 110) responsive to the detection that a portion of the item has one or more predetermined characteristics, the said predetermined characteristics comprising either or both the thickness of the said portion of the item, and the thickness of one or more layers within the said portion of the item, determined by optically-based thickness measuring apparatus (6, 102-108). The item may be a product and the portion of the item may be a sheet of packaging material. The item may be a security document and the portion of the item may be a sheet of security document substrate.

Abstract: Authentication apparatus (1, 100) and methods which authenticate an item (4, 110) responsive to the detection that a portion of the item has one or more predetermined characteristics, the said predetermined characteristics comprising either or both the thickness of the said portion of the item, and the thickness of one or more layers within the said portion of the item, determined by optically-based thickness measuring apparatus (6, 102-108). The item may be a product and the portion of the item may be a sheet of packaging material. The item may be a security document and the portion of the item may be a sheet of security document substrate.

Abstract: There is described a method of tracking an article (30) and protecting it against tampering and counterfeiting, the method comprising the steps of providing an article; providing a film (1c) for wrapping or labelling the article; marking the film with a code (5c); defining an area of interest (35) on the article or the film; wrapping or labelling the article with the film so that the code at least partially overlays the area of interest to define a tracking zone in the region of the at least partial overlay; imaging the tracking zone of the wrapped or labelled article; and storing the imaged date for identifying the article. There is also described, use of a frequency-tripled neodymium-doped yttrium aluminium garnet (nd:YAG) laser in marking a code (5c) on a film (1c), the code comprising an at least partly random pattern of perforations (21, 23, 25).

Abstract: A method of authenticating a polymer film comprises measuring the thickness of a layer therein by white light interferometry and/or measuring the birefringence of a layer therein. The method, and devices to carry out the method, may be used in security applications, for example to test for counterfeit bank notes.